1. Field of the Invention
The present invention relates to a focusing apparatus for auto-focusing on an object to be photographed based on the object information and a method for controlling the focusing apparatus.
2. Description of the Related Art
Conventionally, in a focusing apparatus included in a video camera or the like, the most commonly used method for auto-focusing is to detect an auto-focus (AF) evaluation value representing sharpness from an image signal obtained by photoelectrically converting an object image using an image sensor, and to control a focus lens position so as to maximize the AF evaluation value. Hereinafter, this focusing method is referred to as a television-auto focus (TV-AF) method.
However, using this TV-AF method, there has been a problem that does not focus on a person to be a main object but on a background with high contrast due to photographing conditions and object conditions. In order to solve this problem, an imaging apparatus with a face recognition function is known. Recently, a method of setting an AF area so as to contain a recognized face area to execute focus detection (Japanese Patent Application Laid-Open No. 2006-227080), a method of detecting eyes of a person to execute focus detection based on its result (Japanese Patent Application Laid-Open No. 2001-215403) and the like have been proposed.
In a focus detection method using the above-described face recognition function, an AF area is set to a face area when the face of a person is recognized and when it is not recognized, an AF area is set to be a predetermined area, thereby executing focus detection. Thus, when the face of a person is consistently recognized, focusing is stably performed on a person. However, practically, if a change in the object occurs, for example, when a person turns away, closes her/his eyes, or a camera shake during photographing occurs, accuracy of recognition of the face decreases. In the conventional method, under the conditions described above, since an area to detect an AF evaluation value is frequently changed between when a face is recognized and when it is not recognized, an AF evaluation value is significantly fluctuated. Thus, stable focusing cannot be obtained. Particularly, when taking a motion picture, the person to be photographed most probably keeps moving and the influence becomes more noticeable.